Glycolysis is essential for sperm energy production and motility. Several enzymes in this central metabolic pathway have isoforms that are only found in developing spermatogenic cells and mature sperm. These novel isoforms, particularly glyceraldehyde 3-phosphate dehydrogenase-S (GAPDHS), are promising contraceptive targets because they are specific to male germ cells, essential for sperm motility and male fertility, and are well suited to pharmacological inhibition. Furthermore, our preliminary studies provide evidence that GAPDHS can be differentially inhibited with small, drug-like compounds. The objectives of this proposal are to identify and validate lead compounds that selectively inhibit GAPDHS and to determine if these compounds specifically block sperm glycolysis, ATP production and motility. Our goal is to facilitate the development of a post-testicular, non-hormonal contraceptive with little potential for systemic effects that directly blocks sperm function. Specific Aim 1 - Use high throughput screening (HTS) and virtual screening approaches to identify hit compounds that selectively inhibit human GAPDHS. Specific Aim 2 - Determine if compounds that inhibit recombinant GAPDHS (Specific Aim 1) also inhibit GAPDHS activity, ATP production and motility in mouse and human sperm. Specific Aim 3 - Analyze structure-activity relationships (SAR) of validated hit compounds to identify and develop contraceptive leads that are potent and selective inhibitors of GAPDHS. Targeting sperm-specific glycolytic enzymes represents a novel approach to male contraception. Experiments addressing the aims of this proposal will be performed by a unique team of investigators with documented expertise in the analysis of sperm function and inhibitor design using drug discovery tools such as HTS, medicinal chemistry and cheminformatics. This combination of capabilities promises to yield valuable new information with a high probability of leading to the development of a novel male-specific contraceptive. PUBLIC RELEVANCE: The goal of this proposal is to develop a safe and effective male contraceptive that directly blocks sperm function. The availability of better contraceptive options for men would facilitate global public health and family planning efforts.